1. Field of the Invention
The invention relates generally to an oral composition having a lubricating function. More particularly, the invention relates to a composition for relieving the soft-tissue disorders associated with xerostomia, the active ingredient of the composition being a beta-glucan polymer.
The invention also encompasses a method of treating xerostomia comprising administering to an affected individual a lubricant composition containing a beta-glucan polymer in an orally acceptable vehicle.
2. The Prior Art
Xerostomia commonly known as "dry mouth" is a condition in which the salivary glands do not produce sufficient quantities of saliva. This causes discomfort which can in some cases be quite severe. Without saliva, the mouth burns and the throat and tongue can undergo radical changes. Teeth can decay rapidly and the tongue can become smooth, cracked and vulnerable to infection.
The mouth is one of the body areas most exposed to the external environment. Normally, mucous forms a continuous protective layer in the nose, mouth and throat. A patient suffering from xerostomia not only has decreased fluid in the mouth, but also an insufficient quantity of mucoproteins and mucopolysaccharides to hold fluid in contact with the cells and create a barrier to irritation and infection.
Cases of xerostomia may vary from the mild, in which only slight dryness is experienced, to severe cases in which the patient will have serious problems with mastication, swallowing, digestion, speech, and the like. As noted in U.S. Pat. No. 4,438,100 to Balslev et al., there are a number of causes of xerostomia, including the physiological (e.g., age, menopause, postoperative conditions, dehydration), as well as the psychic (nervousness). The reasons for mouth dryness may also be pharmacological (e.g., as a common side effect of many medications, including anti hypertensives, diuretics, anti-arthritics and anti-depressants) or as a result of radiotherapy. The most severe cases of xerostomia are caused by radiation therapy after head and neck surgery and by autoimmune diseases such as lupus, Sjogrens Syndrome, and rheumatoid arthritis.
Until recently, the treatments for xerostomia have had significant drawbacks. For example, symptoms of mild xerostomia can be somewhat alleviated by consumption of fluids, hard candy and throat lozenges. Because of the susceptibility of xerostomia patients to tooth decay and gum disease, however, the increased sugar intake associated with conventional candy and lozenges is of real concern. In addition, fluids or candy are typically not effective with more severe cases of xerostomia, nor do they provide long-lasting relief with mild cases.
Artificial saliva and salivary substitutes have been proposed as palliative treatments for the symptoms of xerostomia, which preparations have physical and chemical properties that simulate those of natural (human) saliva.
Artificial salvias of the prior art include compositions which contain ions that mimic those found in natural saliva; glycerin, as well as carboxymethylcellulose-based preparations to provide the proper level of viscosity. Fluoride ions are sometimes included to prevent demineralization of tooth enamel. These compositions have not found wide acceptance as many patients find, that such preparations are irritating or distasteful, and that their lubricating effect is of relatively short duration. This lack of wide acceptance is believed due, at least in part to the fact that the artificial saliva preparations of the prior art do not fully possess the rheological characteristics of natural saliva which are responsible for natural saliva's lubricating effect. An article entitled "Lubrication and Viscosity Features of Human Saliva and Commercially Available Saliva Substitutes", M. N. Hatton et al, J. Oral Maxillotac. Surg. 45, 496-499 (1987), contains a full discussion of the problems associated with the presently available commercial saliva substitutes in the treatment of individuals with diminished salivary gland function.
In view of the problems which occur when salivary secretion is deficient, it will be understood that it would be most desirable to have an oral lubricating composition for human use, to relieve the above-mentioned discomforts and inconveniences incurred by xerostomia or by a greater or lesser tendency to dryness of the mouth. Such a composition should have rheological properties which are as close to the properties of the natural salivary secretion as possible and exhibit improved lubricity so as to provide to the patient long term relief from the symptoms of xerostomia or dry mouth.